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Q: GS750B muffler

GS750

Forum Mentor
Gday all, Just after some suggestions / ideas please.

sorry about my ramblings but please stick with me while I get my questions across.

Ok, my bike is the 77 GS750B and has the wiseco 850bb kit fitted, rejetted (cant remember the jet sizes, I think its 112.5 mains from rough memory but I have recently upended my office and now can not find my sheet with the exact specs of my bike for various things.

Ok, the when I got the bike it had a 4-1 pipe set and a alloy can style muff of unknown brand but it is VERY large and had a lovely note to it, though the baffle is a rolled cage with small holes in it.

About a year ago I placed a 2nd hand tranzac muff (also alloy can style) onto the bike and it had a totally different sound, it should sound different (quieter) too because it is about 1/3 less in size and the bike sounds like a sewing machine it is that quiet but felt much more responsive on the throttle.

I found that the jetting was fine with both systems which was pretty surprising as the tranzac is much smaller in the baffle tube (restriction) .

Well, I recently decided to send the whole exhaust away for coating and had to strip the baffle out and remove the fibreglass wool from it so they can coat it. I found that the baffle tube is all but gone, eaten away :O And replacement is unavailable as they stopped making them years ago now.


Well I dont know what to do now because I liked the note of the unknown brand can, but the tranzac provided more throttle response.

I did google about the muffler but didnt really find anything that could firm my opinion up :'(

Does anyone out there have any suggestions? I may have to grab a new muff but dont know whats out there to suit, or a reasonable price ( I did find some up to OMG $1200 during my google search lol)
 
The baffle shouldnt be that hard to replicate no? Some steel round hole mesh and a spot welder. Pack it with stainless steel wool. Fiberglass will hold in moisture and cause it to rust out faster.
 
The baffle shouldnt be that hard to replicate no? Some steel round hole mesh and a spot welder. Pack it with stainless steel wool. Fiberglass will hold in moisture and cause it to rust out faster.

Thanks for that. I thought about making something up but It is punched metal, lots of litle holes I hope to get some photos up soon of the 2 mufflers.

Also, how does the different metals go for galvanic reaction?? The casing is alloy, the baffle is (probably) mild steel coated in something like zinc? and if I put stainless in there Im not sure how that goes (I am only going from my experiences with mixing metals in boats)
 
Here are some clickable thumbnails of the 2 mufflers I am talking about.


4-1 pipes, outlet id:46.5mm and od:53.9mm


Generic and Tranzac mufflers side by side (both are inlet size: 55.0mm


Generic can baffle


Tranzac baffle





Generic can outlet diameter 50.1mm


Tranzac outlet diameter 31.1mm





Tranzac baffle inlet reducer


Tranzac baffle reducer


Tranzac baffle diameter


Tranzac rotten baffle



The Generic can is thinner in the outside wall and the alloy discolours much faster (harder to keep clean)


The Generic can is the one which was fitted to my bike when I bought it and has a nicer note to it than the Tranzac but I have also rebuilt the motor (about 3 years ago now??).

The Tranzac is much quieter and you can hear more engine noise than exhaust noise but it definitely feels more responsive with the Tranzac than the Generic.

Caby jetting did not need changing (only mixture screw) which was pretty surprising as the tranzac is much smaller.


I dont want to run the exhaust too open as I dont want to drop valves or cause other engine damage.
 
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